What sim racers have you played recently/before? GTS is in a much better state now than at launch. It's a very... serious game, so if you're questioning finding 'the fun' I might try to borrow it or something to try. The online is still the meat of the game and it's a very honour based, serious affair. You need to wait for time slots for the races (meaning you can't always just jump into a race - you often need to wait 10/15 minutes for your time slot to arrive) and the races are very much about driving 'properly' and maybe moving from 10th to 8th or something, not necessarily all about winning.
I think the online is great for what it's worth. The racing is very clean. I do think that, despite recieving a bunch of updates since launch, it's still quite light on content. It's got loads better but it still has less tracks than some of its conpetitors and the cars still lean heavily towards racing cars (you can tell I'm not a car man) rather than everyday cars. To be fairly brutal, it still (to me) feels like they're adding stuff that it should've really launched with. Kudos to them for keeping supporting it though.